Conventionally, transmissive liquid crystal display devices are known as image display means. The transmissive liquid crystal display device is provided with a non-self-luminous liquid crystal panel and accordingly requires a backlight device.
A backlight device including a cold cathode fluorescent lamp (CCFL) as a light source has been used conventionally. Recently, however, a backlight device including a LED as a light source is widely used, which is free from disadvantages of a cold cathode fluorescent lamp, such as environmental pollution caused by mercury, or slower response speed.
In addition to solving the disadvantages of a cold cathode fluorescent lamp, the backlight device including a LED as a light source can also achieve a partial drive such as local dimming (area control) to improve a contrast ratio of an image. The local dimming will be described below.
The local dimming refers to processing for adjusting a backlight intensity of each of a plurality of areas (light intensity control areas) into which a liquid crystal panel is divided, on the basis of luminance components of image data of each of the plurality of areas. That is, in the liquid crystal display device which employs local dimming, a backlight intensity of an area displaying a bright image can be increased, whereas a backlight intensity of an area displaying a dark image can be decreased. It allows the liquid crystal display device which employs local dimming to display an image of a higher contrast ratio in which a bright image region is displayed brighter, and a dark image region is displayed darker.
However, the liquid crystal display device which employs local dimming has a disadvantage, which will be described below, in a case where one area displaying white and black images, and another area displaying only a black image are adjacent to each other, for example. That is, a backlight intensity of the area displaying white and black images is adjusted to a value in accordance with the white image (an image with high luminance components), whereas a backlight intensity of the area displaying only a black image is adjusted to a value in accordance with the black image (an image with low luminance components). This leads to a difference in brightness of displayed black between one area and another area, resulting in an unnaturally-appearing image being displayed in which a boundary between the areas is conspicuous. In order to avoid such a disadvantage, a liquid crystal display device has been proposed, which employs processing in which, after backlight intensities of respective areas are calculated on the basis of a local dimming technique, the backlight intensities of the respective areas are corrected so that no area has a light intensity differing greatly from those of adjacent areas (hereinafter referred to as a “light intensity correction”). Patent Literature 1 discloses an example of such a light intensity correction.